Creatine with caffeine?

The effects of a high dosage of creatine and caffeine supplementation on the lean body mass composition of rats submitted to vertical jumping training

We demonstrated that supplementation with high combined doses of creatine and caffeine did not affect the LBM composition of either sedentary or exercised rats. However, caffeine supplementation alone reduced the percentage of fat in the carcass. In addition, the employed model of power training increased the percentages of water and protein and reduced the fat percentage in rats.

One of the main observations of our study was that animals supplemented with creatine or creatine plus caffeine did not present increased water retention in skeletal muscles (carcass). It is suggested that creatine supplementation leads to intramuscular water accumulation caused by its high osmotic power [7, 33]. Our results do not corroborate such hypothesis and are consistent with the similarity of body weight among our experimental groups as an increase in water retention in response to creatine ingestion might have augmented body weight [13, 34]. Even though the methods of weighing were indirect, this lack of increase in body weight caused by creatine supplementation has been reported elsewhere [2, 11, 29].

Despite the fact that caffeine exerts a slight diuretic effect [15], which could have reduced water content, contrasting the effects of creatine [35], our study revealed that caffeine ingestion did not affect the percentage of water in the lean body mass. Similar results were found by Vanakoski et al. [36], although in our experiment, caffeine dosage was 2.14 times higher.

So caffeine and creatine together did not affect body weight, but caffeine alone did. They also did not observe a water weight increase in muscles like is assumed with creatine use.

Our observation that creatine or creatine plus caffeine did not affect the protein percentage of lean body mass demonstrates the absence of differences in body weight among our experimental groups. The increased in muscular mass in response to creatine ingestion [5, 11, 34, 35] may be due to the increased water retention in muscles [13]. However, such effect was not observed in the present study. Similar results were found by others [2, 29, 39]. When measuring urinary nitrogen, Jowko et al. [40] verified that creatine did not affect the retention of body nitrogen, suggesting that creatine would not increase protein incorporation. In the present study, even though creatine doses were very high, it did not affect protein percentages in the carcass of creatine supplemented groups.

They also did not observe an effect on urinary nitrogen, which they say points to evidence that creatine is not increasing protein incorporation into muscles.

Our results revealed that high-dose caffeine supplementation reduced the fat percentage of the lean body mass as compared to creatine ingestion, independently of the exercise training. It has not been mentioned the direct effect of creatine on skeletal muscle fat [2, 11]. However, the ingestion of caffeine may increase the turnover and mobilization of free fatty acid [22, 41, 42] and save muscular glycogen storages [22], which would result in reduced body weight [42]. Caffeine intake increases the basal metabolic rate and catecholamine release [41, 43]. Caffeine may also inhibit the activity of the phosphodiesterase enzyme, which increases the levels of AMPc and reduces the activity of hormone-sensitive lipase, leading to higher lipolysis [44]. However, we found no differences in body weight among the groups SPl and EPl, as compared to SCaf and ECaf, respectively. We also demonstrated that the group SCaf presented higher body weight than ECaf and that the exercised animals exhibited lower body weight, as compared to the sedentary animals. Therefore, such reduction in the percentage of fat in the carcass of animals supplemented with caffeine may indicate the interference of exercise instead of caffeine ingestion.

They did notice lowered fat percentage in the high-caffeine group, but not the creatine group.

In the present study, neither supplementations nor exercise training affected the excretion of urinary creatinine during the first week. In the second week, the creatinine from the groups creatine or creatine plus caffeine was higher than that from the placebo group, and also higher as compared to the first week. On the other hand, urinary creatinine decreased. Thus, the significance of creatine and creatine plus caffeine effects from the second week has disappeared. These results indicate that the ingestion of high doses of creatine (0.431 g·kg) during the load phase promoted increased excretion of urinary creatinine via a non-enzymatic reaction, as demonstrated by other authors [13, 29, 45]. Our data also suggest that the load phase could be more important in increasing body creatine storages, since after the phase of creatine maintenance (6th week), urinary creatinine excretion was reduced.

They also found the loading phase was more important than the maintenance phase at increasing creatine stores.

Finally, caffeine ingestion did not affect creatinine excretion. Such finding suggests that caffeine ingestion had no effect on creatine pharmacokinetics. However, our data do not allow us to substantiate such suggestion as we did not measure the muscular content of creatine and its clearance. This is a limitation of this study and requests further investigations.

So caffeine does not alter the pharmacokinetics of creatine. If there is a mechanism in there blocking some of the ergogenic effects of creatine, those are not related to preventing it from absorbing or causing it to excrete in higher amounts. This is just one study, though. So we can't really make too many conclusions on it. The one I can make is that caffeine is not reducing the amount of creatine in your system. So I would be inclined to assume that creatine is still having benefits in the body when combined with caffeine. I can't think of a mechanism caffeine would be using to block creatine's effects. Examine also has an article on it.

https://examine.com/nutrition/does-caffeine-counteract-creatine/